Inhalation activatable dispensers for use with aerosol container assemblies are known, their general purpose being to afford proper co-ordination of the dispensing of a dose of medicament with the inhalation of the patient thereby allowing the maximum proportion of the dose of medicament to be drawn into the patient's bronchial passages. Examples of such dispensers are described in British Patent Specification Nos. 1,269,554, 1,335,378, 1,392,192 and 2,061,116 and U.S. Pat. Nos. 3,187,748, 3,456,644, 3,456,645, 3,456,646, 3,565,070, 3,598,294, 3,814,297, 3,605,738, 3,732,864, 3,636,949 and 3,789,843 and German Patent No. 3,040,641.
European Patent No. 147028 discloses an inhalation activatable dispenser for use with an aerosol container in which a latch mechanism releasing vane is pivotally mounted in an air passage between an aerosol outlet valve and a mouthpiece, which latch mechanism cannot be released if force to activate the dispenser is not applied before a patient inhales.
The dispenser generally comprises a housing having a mouthpiece and an air passage therethrough terminating at the mouthpiece, the housing being adapted to receive an aerosol container and having a support block with a socket adapted to receive the stem of the valve of the aerosol container and a through orifice communicating between the socket and the air passage, and latch means having parts movable between an engaged position in which movement of the container and the support block toward each other upon the application of a force to bias the container and the support block toward each other is prevented and a release position in which movement of the container and the support block toward each other in response to said force is permitted causing the stem to move to its inner discharge position, the latch means comprising a vane mounted on the housing in the air passageway between the orifice and the mouthpiece for movement toward the mouthpiece under the influence of inhalation through the mouthpiece to release the latch means in which the vane moves toward the mouthpiece from a blocking to a non-blocking position with respect to the passageway in response to inhaling at the mouthpiece and releases the latch means only during the application of said force to bias the container and support block toward each other.
Co-pending International Patent Application No. PCT/US90/02412 (Publication No. WO90/13328) discloses a dry powder inhalation device comprising a housing defining a chamber in communication with a patient port in the form of a mouthpiece or nasal adaptor, and an elongate carrier bearing a powdered medicament, the device being constructed and arranged such that areas of predetermined size of the elongate carrier may sequentially be exposed within the chamber, the device comprising one or more air inlets such that when a patient inhales through the patient port an air flow is established from the air inlet(s) to the patient port through the chamber such that particles of the powdered medicament of respirable size from said exposed area of the elongate carrier are entrained within the air flow.
The dry powder inhaler is capable of delivering multiple, uniform doses of a medicament to a patient. The device is simple to operate and does not require the patient to insert capsules of medicament or rely upon a separate reservoir of medicament in order to load the device for use. The medicament is generally preloaded on an elongate carrier, sections of which are sequentially exposed in the chamber for dispensing the medicament. The elongate carrier is preferably in the form of a tape having an array of depressions or microdimples holding micronised medicament and may be conveniently loaded on a spool (in a similar manner to a photographic film) or in a cassette (in a similar manner to an audio cassette). A preferred carrier is disclosed in European Patent Publication No. 0455463.
The device includes means for advancing the elongate carrier through the chamber to sequentially expose areas of the carrier for release of medicament during inhalation by the patient. The means for advancement may take a variety of forms depending upon the type of elongate carrier and whether the exposed areas of carrier are to be retained within the device. For example, tapes webs and belts may include a series of apertures which are engaged by one or more sprocketed guide wheels or rollers in a similar manner to a camera or printer. Alternatively, or in addition, the carrier may be wound on a take-up spool, rotation of the spool directly or via a drive belt causing the carrier to advance. The device may also include means for tensioning or otherwise maintaining the exposed area of the carrier within the chamber during inhalation by the patient.
The elongate carrier may be advanced into the chamber prior to inhalation by the patient or the carrier may be advanced into the aerosolisation chamber during inhalation to protect the powdered medicament from premature exposure.
In the preferred embodiment the elongate carrier is stored in a cassette both before and after exposure. The cassette may comprise one or preferably two spools together with idlers or other rollers and include an exposure frame positioned within the chamber, through which the carrier is advanced. The cassette may be removable to allow the device to be recharged with a new cassette. However, it is not essential for the exposed areas of the carrier to be retained within the device and spent carrier may be advanced to the exterior of the device through a slot in the housing whereupon disposal may be effected by the patient, optionally with the aid of a cutting edge. This arrangement is particularly suitable for a tape carrier which has transverse perforations to facilitate tearing off spent carrier.
The device preferably additionally comprises means for releasing medicament of respirable size from the exposed area of carrier independent of the patients' inspiratory effort. The medicament release means overcomes the binding of the medicament particles to the carrier by mechanical effort e.g. impaction, vibrations, gas flow etc. or electrostatically.
The means for releasing medicament from the carrier during inhalation is preferably triggered in response to the patient inhaling in order to avoid the patient having to synchronise inhalation and actuation of the release mechanism. Airflow detection may conveniently be accomplished by means of a movable vane positioned within the chamber or patient port, motion of the vane causing actuation of the release mechanism. Such a vane may also be constructed to prevent a patient exhaling through the device and/or to prevent exhaled air from reaching the stored carrier thereby avoiding any problems associated with moisture.